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| report [2016/07/12 22:46] – [2.6 Components of a geodesic dome] team4 | report [2016/08/29 17:45] (current) – [2.7 Materials] team4 |
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| </WRAP> | </WRAP> |
| </table> | </table> |
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| == - Different types of actuators == | |
| **Pneumatic actuators** | |
| * **Advantages:** The benefits of pneumatic actuators come from their simplicity. Most pneumatic aluminum actuators have a maximum pressure rating of 10.5 bar which translate into approximately 133.5N to 33 361N force. Steel actuators have a maximum pressure rating of 17 and they generate forces ranging from 222N to 171 100N; Pneumatic actuators generate precise linear motion by providing accuracy within 2.5mm and repeatability within 0.025mm; Typical applications involve areas of extreme temperatures. A typical temperature range is -40°C to 121°C. In terms of safety and inspection, by using air, pneumatic actuators avoid using hazardous materials. They meet explosion protection and machine safety requirements because they create no magnetic interference due to their lack of motors; | |
| * ** Disadvantages: ** Pressure losses and air’s compressibility make pneumatics less efficient than other linear-motion methods. Compressor and air delivery limitations mean that operations at lower pressures will have lower forces and slower speeds. A compressor must run continually operating pressure even if nothing is moving; To be truly efficient, pneumatic actuators must be sized for a specific job. Hence, they cannot be used for other applications. Accurate control and efficiency requires proportional regulators and valves, but this raises the costs and complexity. | |
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| **Hydraulic actuators** | |
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| * ** Advantages: **Hydraulic actuators are rugged and suited for high-force applications. They can produce forces 25 times greater than pneumatic cylinders of equal size. They also operate in pressures of up to 275 bar; Hydraulic motors have high horsepower-to-weight ratio by 0.2 to 0.45 hp/N greater than a pneumatic motor; A hydraulic actuator can hold force and torque constant without the pump supplying more fluid or pressure due to the incompressibility of fluids; Hydraulic actuators can have their pumps and motors located a considerable distance away with minimal loss of power. | |
| * ** Disadvantages: ** Hydraulics will leak fluid. Like pneumatic actuators, loss of fluid leads to less efficiency. However, hydraulic fluid leaks lead to cleanliness problems and potential damage to surrounding components and areas; Hydraulic actuators require many companion parts, including a fluid reservoir, motors, pumps, release valves, and heat exchangers, along with noise-reduction equipment. This makes for linear motions systems that are large and difficult to accommodate. | |
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| ^ Material ^ Properties ^ R-Factor (K*m<²/W) ^ | ^ Material ^ Properties ^ R-Factor (K*m<²/W) ^ |
| | Clear marine vinyl[(pacificdomes2016)]| Flame resistant, Waterproof, Highly resistant to mildew, durable| 0,61 | | | Clear marine vinyl[(PacificDomes2016)]| Flame resistant, Waterproof, Highly resistant to mildew, durable| 0,61 | |
| | Polyethylene plastic[(Greenhousecatalog2016)]| Inexpensive, not very durable| 0,83 | | | Polyethylene plastic[(Greenhousecatalog2016)]| Inexpensive, not very durable| 0,83 | |
| | Solexx twin-wall polyethylene cover 3,5mm [(solexxcovering2016)]|Strong, accelerates plant grow, good insulation, good durability| 2,10 | | | Solexx twin-wall polyethylene cover 3,5mm [(solexxcovering2016)]|Strong, accelerates plant grow, good insulation, good durability| 2,10 | |
